tim brick managing director, arroyo seco foundationthe current system of sediment management in...
TRANSCRIPT
Tim Brick
Managing Director, Arroyo Seco Foundation
Standard Equipment Until 1956
Now we recycle . . .
That’s sustainability.
Now we have 1.2
gallon toilets
That’s sustainability
We used to throw away our waste water
Now we recycle more than 350,000
acre feet a year.
That’s sustainability.
But why do we still treat storm water and sediment as waste products???
Six hundred thousand acre feet of storm water each
years flows to the ocean from Los Angeles County
• It provides habitat for fish
and aquatic species
• It nourishes rivers and
beaches
• It fills our valleys and the
coastal plain
• It can be used for
construction purposes
Rivers don’t just transport water. A key function is to transport sediment.
It’s time to take a new look at how we
manage sediment and storm water.
It’s time to stop starving the streams
and beaches of Southern California.
- Make Room for the River
The dramatic geology of
the Los Angeles Basin
The Transverse Range
Alluvial Valleys
Steep erosion-prone
mountains ringing a
dense urban area
These rapidly rising
“teenage” mountains are
rushing to get to Long
Beach . . . in geologic time
We’ve crowded the foothills
We’ve paved our
communities
• Homes and business have
encroached on the floodplain
• We put out streams and
rivers in a concrete strait
jacket to speed the flow of
storm water to the ocean
Driven by the promises of development and imported water
• And neither is
sediment
• But the Sediment
Buildup Is
Have Human Efforts Aggravated the Flood Threat???
The Flood
of 1914
• A watershed
• A canyon
• A stream
• A tributary of LA River
• A transportation corridor
• A parkway
• A cultural haven
• Communities united
. . . The most celebrated canyon in Southern California
Hahamongna is the
vital link
between the Upper
and Lower Watershed .
. .
between the mountains
and the city
Gateway to the
Raymond Basin
Hahamongna –
Total Sediment To Be Removed
(Next 20 Years)
• 14 Dams
• 162 Debris Basins
82+ Million Cubic Yards
Sediment Placement Site Capacity - 11.6
Million Cubic Yards
Cost per cubic yard: $30-60
Total Cost: $3-5 Billion
The Current Program
Devil’s Gate Dam
The first of the
LA County flood
control dams
built in 1920 for
flood protection
and water
conservation
162 Sediment Basins
• All of these facilities were developed before NEPA, CEQA, etc.
• There has never been a thorough review conducted on their environmental
impacts
Sediment, water
and debris move
down gradient
through the
watershed towards
the ocean, creating
dynamic riverine
and riparian habitat
and replenishing
beaches along the
way.
The Natural Process
Restoring the Arroyo chub
• We developed the floodplains, alluvial fans, and foothills with industry
and housing.
• We installed engineered solutions such as flood control dams and debris
basins and channelized runoff to prevent property loss and damage.
• We’ve broken the hydrologic cycle precluding the movement of materials
and nutrients out of the upper watershed towards beaches.
How It Happens Today – Thwarted Natural Processes
• Rain Barrels
• Rain Gardens
• On-site Retention
• Permeable Pavement
• Unpaving
How many tons
of sand are lost
to the beaches
each year???
“And it never failed that
during the dry years the
people forgot about the
rich years, and during the
wet years they lost all
memory of the dry years.
It was always that way. “
John Steinbeck
The current system of sediment management in Southern California is economically and environmentally unsustainable
It will:
• cost $3-5 billion in the next 20 years
• aggravate human health risks (heavy equipment emissions, noise,
traffic, dust, precludes natural flushing events)
• rob downstream landscapes and ecosystems of their essential
building blocks (fine sediments, sands, gravel, nutrients, etc.)
And it won’t solve the problem
TIME FOR A CHANGE IN PARADIGM!
Developing a Sustainable Integrated Sediment Management Program
• Review the effectiveness and
viability of flood control
methods
• Review the environmental
impacts of the dams and
ditches approach
• Conduct educational outreach
to the public to improve
understanding about natural
processes.
TIME FOR A CHANGE IN PARADIGM!
Developing a Sustainable Integrated Sediment Management Program
• Pursue sediment management
options that safely mimic natural
processes from the top of the
watershed to the bottom
(sluicing, stream and floodplain
restoration, and others).
• Promote SMART development
and re-development
• Landuse regulations (green
buffers, density, proximity to
wildlands, defensible space,
distance from geologic
hazards)
• Mandate low-impact/Green
building design
What You Can Do: • Get Informed • Support River Restoration • Visit Hahamongna • Talk to Local Officials • Subscribe to Arroyo_Seco_News • Support the Arroyo Seco Foundation & Save Hahamongna
Tim Brick
Arroyo Seco Foundation - http://www.arroyoseco.org
Save Hahamongna - http://www.savehahamongna.org